docs: def merge(self, other):
          """Merge another ontology into the current one.
  
          Raises:
              TypeError: When argument is not an Ontology object.
  
          Example:
              >>> from pronto import Ontology
              >>> nmr = Ontology('tests/resources/nmrCV.owl', False)
              >>> po = Ontology('tests/resources/po.obo.gz', False)
              >>> 'NMR:1000271' in nmr
              True
              >>> 'NMR:1000271' in po
              False
              >>> po.merge(nmr)
              >>> 'NMR:1000271' in po
              True
  
          """
          if not isinstance(other, Ontology):
              raise TypeError("'merge' requires an Ontology as argument,"
                              " not {}".format(type(other)))
  
          self.terms.update(other.terms)
          self._empty_cache()
          self.adopt()
          self.reference()